 Photofrin was first approved in the 1990s as a sensitizer for use in treating cancer via photodynamic therapy, PDT. Since then a wide variety of dye sensitizers have been developed and a few have been approved for PDT treatment of skin and organ cancers and skin diseases such as acne vulgaris. Porphyrenoid derivatives and precursors have been the most successful in producing requisite singlet oxygen, with photofrin still remaining the most efficient sensitizer, quantum yield equals 0.89, and having broad food and drug administration, FDA, approval for treatment of multiple cancer types. Other porphyrenoid compounds that have received approval from US FDA and regulatory authorities in other countries include benzoporphan derivative monoacid ring A, BPDMA, metatetra, hydroxyphenyl, chlorine, MTHPC, anispartal chlorine E6, NPE6, and precursors to endogenous protoporphan 9, PPX1, 5, Aminoleval. This article was authored by Harold S. Freeman and Alexandra B. Ormond. We are article.tv, links in the description below.